Concrete floor construction



ELLS. CONCRETE FLooRtozNsTHucTloN.

H. L. w

APPLICATION FILED DEC-22. 1921.

Patented spn 25, i922.

H. L. WELLS.

CONCRETE FLOOR CONSTRUCTIDN. APPLICATION FILED DEc.22. I92I.

Patented Sept'. 26, 1922.

2 SHEETS-SHEET 2.

Patented l ept. 2id, llQZZ.

g naar HEWITT L. WELLS, OF WASHING-TON', EHSTRIECT OF COLMBA, .ASSGNOR T0 T-BEAM ENGINEERING COMPANY, OF VASHlINGTON, DISTRICT 0F COLUMBII-LVA CORPORA- concentre .rnoon consranorron.

Application filed December 22, 1921. Serial No. 524,052.

To all whom t may concern:

Be it known that l, l-lnwrrr L. lWnLLs, of Washington, in the District of Columbia, have invented certain new and useful lmprovements in Concrete Floor Construction; and l do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it'appertains to make and use the'same.

My invention relates to concrete floor construction and particularly such as are reinforced in two directions and supported on reinforced concrete girders and columns or concrete and tile encased steel girders and columns. Because of the relative economy and simplicity of construction the flat slab type of floor has been largely used but vit has been found, in analyses of suoli floors reinforced in two directions, that there are certain weaknesses which must be overcome to insure against initial failure and properly and more adequately distribute the reinforcement to further increase their load carrying capacity. lt has been noted inA such analyses, and especially in loading tests on slabs of -this type, that high stresses are developed in the region of the corners of the panel adjacent to the column being indicated by openings or cracks in the bottom of the concrete slab and which radiate from the edges of the columns toward the center of the slab or panel. investigation further discloses that the reinforcing bars in the bottom of the slab in proximity and close to the sides of the beams are not subject to stress and are not vtherefore of prime necessity to the strength of the structure and may therefore be eliminated lt isthe object of my invention to produce a concrete floor construction wherein the slab shall' be of a minimum thickness commensurate with the bending moment 'and deflection 'values and one embodying a proper and adequate arrangement and distribution of bar reinforcement in a manner to overcome the diiii culties heretofore encountered, and such a floor construction wherein, within certain limits of span and loads, a lesser quantity of reinforcing material shall be required without detracting from the strength of the structure.

ln the drawings, Figure l is a top plan view showing the arrangement of the reinforcing elementsfor a floor panel or slab of solid concrete supported on reinforced concrete girders on four sides of the panel. Figure 2 is a sectional view through the center line of the panel shown in Figure l. Figure 3 is an enlarged plan view of a column with the reinforcing elements forv the corners of the panel. Figure l is a vertical section of a portion of two adjacent panels at their point of support on .beams and column to indicate the arrangement of reinforcing elements at that'point.

As is well known, concrete floors have heretofore been reinforced by bands of steel bars A and B, the bars A, forming oneseries, being arranged at right angles to the bars B, which form a second series, all of the bars of each series being supported by reinforced girders or beams, indicated at C, the ends of thebars framing into or eX- tending over the beams and overlapping the bars of adjacent panels. lt has been the practice heretofore to place the reinforcement the full width of the panel, the outside bars of each bandbeing located close to the side of the respective girder. A. study of the test data and conclusions drawn therefrom has indicated that the tensile stress inthe bottom of theslab varies from a maximum at the center to zero near -the beam parallel to the reinforcing members. rllie steel may therefore be advantageously distributed over only a part of the width of the slab. lt is proposed to distribute most or all of the steel required in the vmiddie three-iifths of the panel, although, to cover cases of possible unbalanced loading,

80% of the steel may be equally distributed rlhe necessary negative reinforcement .here tofore supplied by the bent up and extended ends of the slab bars lying at the outer edges oit the bands is thus taken care of by the combined stirrup and continuity reinforcement.

To provide against the initial 'failure by tensile stresses occurring at the bottom ot the slab at the corners oit the panels l provide a reinforcing unit which is arranged so as to intersect the radii ot the column Within the angle defined by the supporting beams, or othernf'ise stated a reinforcing element fitting Within the corner between right angularly disposed beams or other supporting meinbei-. ln Figure 23, three different forms ol reinforcement are shown, l being a single bar bent back upon itseliE a number of times with the several lengths so termed lying in spaced parallelism. 2 shows a second Yform Where several bars are arranged in spaced relation and so held by a looped cross bar El to which they are appropriately wired, or these several may be held as shown in the third torni, Figure 3, by a single cross bar 4l. ln this Figure 3 l have shown the Vvarious reinforcing elements et the beams in lull lines and have omitted the parts oi the stirrups Dall for the salte ot clearness.

lt is the customary practice to have part of the barsv in eachr beam straight and framed directly into the columns, as indicated` at E While others, shown at F, are bent up and over the column into the adjacent beam to supply continuity. ris will be apparent from an examination olf Fig ures 3 and 4l it is necessary this cer-v nerv reintorcing'element, variously denoted l and 2, shall be easy to install at the point Where so fmuch steel reinforcing is centered and yet must be structurally correct. The character of corner reinforcing described meet'sthese requirements and effectively reinforces the panel at this point.

l' claim as my invention:

l. fr concrete Ydoor including supporting columns, beams spanning'the space between such columns, and a concrete slab having a plurality' ot spaced apart reinforcing ste il bars arranged in two serie" at right angles to each other and supported by said beams, in combination With reinforcing elements at the lbott-.om of the slab in the space adjacent said column defined by beams or other supporting means between columns lying at right angles to each other.

2. A concrete floor including supporting columns, beams spanning the space between such columns, and a concrete slab havinga plurality of' spaced apart reinforcing steel bars arranged in two series at. right angles to each other and supported by said beams, triangular reinforcing units locatedat the bottom oit the slab in the corners thereof adjacen't said columns.

Y 3. A concrete tloor including supporting columns, beams or other supporting means resonant spanning the space between said columns, and a concrete slab having a plurality et spaced apart reinforcing steel bars arranged in tro series at right angles to each other and supported by said beams or supporting means, in combination with a reinforcing frame oi1 steel at the bottoni oi' 'the slab in the space adjacent said column defined by beams or other supporting means between columns lying at right angles to each other.

il. A concrete floor including supporting columns, beams or omer supporting means spanning the space between said columns, and concrete slab having a plurality ot spaced apart reinforcing rteel bars arranged in Ytivo s at right angles to each other and. supported by said beams or snpporting means, in combination with a reinforcing trame formed with space-cl lengths ot steel. nged in paralleli n at the bottom ot the slab in space adjacent col" umn delined by beams or other supporting means columns lyingl at. rigl'it between angles to each other.

5, A concrete floor including supportii'ig columns, beams or other supporting means spanning the space between said columns, and a concrete slab having a plurality of spaced apart reinforcing steel bars arranged in tivo series at right angles to each other and supported by said beams or supporting means, in combination With a reinforcing frame formed with spaced and varying lengths of steel bars arranged in parallelism at the bottom of the slab in the space adjacent said column deiined by beams or other supporting means between columns lying right angles to each other.

G. 5i concrete floor including supporting columns, beams or other supporting means spanning the space between said columns, and a concrete slab having a plurality of spaced apart reinforcing steel bars arranged in tivo series at right angles to each other and supported by said bears or supporting means, in combination with a reinforcing trame termed Yfrom a single steel bar bent to provide a series 'of spaced lengths arranged in parallelism at the bottom of the slab in the space adjacent said column delined by beams or other supporting means between columns lying at right angles to each other.

'i'. A concrete licor including supporting columns, beams or other supporting means spanning the space between said columns, and a concrete slab having a plurality or' spaced apart reinforcing steel bars arranged in tivo series at right angles to each other and supported by said beams or supporting means, in combination With a reinforcing iframe formed from a single steel bar bent to provide a series of spaced and varied lengths arranged in parallelism at the bot tom of the slab in the space adjacent said column delined by beams or other supportlil@ ing means between columns lying at right angles to each other.

8. A concrete iioor including, in combination with supporting columns, beams or other supporting means spanning the space between said columns, and a concreteslab having a plurality of spaced apart reinforcing steel bars arranged in two series at right angles to each other and supported by said beams or supporting means, stirrups formed from a single bar bent to provide double its cross-sectional area at the tops of the beams to provide for the negative tensile stresses at that point, the ends of the stirrups extending to some distance on either side, and a reinforcing element interposed in the space adjacent said column and lying in the bottom of the slab.

9. A concrete iioor including, in combination with supporting columns, beams or other supporting means spanning the space between said columns, and a concrete slab having a plurality of spaced apart reinforcing steel bars arranged in two series at right angles to each other and supported by said beams or other supporting means, each series being of less width than the span between beams paralleling its bars, the series being centrally disposed in such span, stirrups adjacent the end of each beam with their ends bent up and over the top of the beam and extending some distance beyond to provide for negative tensile stresses, and a reinforcing element' interposed in the space adj aeent said column and lying in the bottom of the slab.

10. A concrete floor including supporting columns, beams spanning the space between such columns, and a concrete slab supported by said beams and columns and having a plurality of spaced-apart reinforcing steel bars arranged in two series at right angles to each other, such reinforcing bars being supported by said beams, in combination with corner reinforcing elements for said slabs having each a plurality of lengths formed from a steel bar and arranged in a horizontal lane diagonal to the longitudinal axes oi the supporting beams.

In testimony whereof l have signed this specilication.

HEWITT L. WELLS. 

